This invention relates to improved gauges for measuring precisely the size of a thread.
U.S. Pat. No. 4,417,402 issued Nov. 29, 1983 to Mark Hattan on "Gauging Of Thread Diameters" discloses and claims a unique type of gauge for measuring the size of an internal screw thread in a nut or other internally threaded member. Gauges embodying the invention of that patent are capable of measuring internal threads very accurately and reliably, and doing so in virtually any diameter of thread including very small sizes which can not effectively be measured by many previously proposed types of internal thread gauges. Structurally, a gauge covered by U.S. Pat. No. 4,417,402 includes two gauge elements having similar external threads adapted to project into opposite ends of an internally threaded passage in a nut or the like, with the elements being adapted to be screwed toward one another to a limiting position in which they contact or are otherwise blocked against further relative axial advancement. The gauge elements have indicator portions which extend externally of the threaded passage to locations at which the rotary setting of one of the indicator portions can be read against the rotary setting of the other indicator portion as a measurement of the effective pitch diameter and functional size of the internal thread.